Gas turbine power plant with auxiliary compressor supplying cooling air for the turbine



Dec. 11, 1951 LOMBARD 2,578,481

GAS TURBINE POWER PLANT WITHAUXILIARY COMPRESSOR v SUPPLYING COOLING AIRFOR THE TURBINE Filed Feb. 10, 1947 Mmqys Patented Dec. 11, 1951 UNITEDSTATES PATENT OFFICE Adrian Albert Lombard, Clith-eroe,- England, as-

signor to Rolls-Royce Limited, Derby, England,

a British company Application February 10, 1947, Serial No. 727,519 InGreat Britain March 25', 1946 3 Claims; i

This invention relates to internal-combustion turbine engines of thekind in which air under pressure is delivered by a compressor to one ormore combustion chambers from which the products of combustion flow to aturbine which is coaxial with the compressor and is connected by adriving shaft to the compressorimpeller, the driving shaft having atleast one bearing between the compressor impeller and turbine rotor. Insuch plants, more than one compressor may deliver to the combustionchamber or chambers, and more than one, turbine rotor may be driven bythe products of combustion.

To 0001 the engine structure, air may either be drawn through it by asuction fan or forced through that structure under pressure and thelatter arrangement is preferable since the increase in the pressurearound the main bearings over the atmospheric pressure reduces the oilleakage from the bearings and improves the efficiency of the lubricationsystem. It has been proposed to circulate the cooling air under pressureby bleeding it from the delivery from the main compressor and passing itthrough a cooler to the turbine structure.

The object of this invention is to provide an internal-combustionturbine engine of the kind described with means to improve the coolingof the engine structure.

According to the present invention, an internal combustion turbineengine of the kind described comprises an intermediate casing extendingbetween the compressor and the turbine, which casing houses a supportfor a bearing of the driving shaft between the compressor and theturbine, and accommodates an auxiliary compressor, the rotor of which issupported on and driven by the said shaft, said auxiliary compressorbeing arranged to deliver air under pressure into the interior of theintermediate casing to flow past the said bearing, to cool it.

This arrangement has the advantage that the cooling air has a lowertemperature than with the arrangement referred to above at the samepressure so that the arrangement is more eflicient and it avoids theunbalancing of the how from one side of the main compressor which occurswhen the cooling air is bled from it.

A construction in accordance with the invention wi11 now be described byway of example with reference to the accompanying drawing whichillustrates the application of the invention to an internal-combustionturbine engine in which the impeller of a double inlet centrifugalcompressor is secured on the front end of a main driving 2 shaft and. aturbine rotor is secured on the rear end'of the shaft.

The main driving shaft 1 between the turbine rotor and compressor'impeller is mounted in a front main bearing 2 immediately in front ofthe compressor impeller 3, a centre main bearing 4 to the rear of theimpeller and a rear main bearing ii immediately in front of the turbinerotor 6. The rear bearing 5' is mounted in a housing 1 carried by thesmaller end of a frusto-conic'al intermediate casing 8 through which theshaft I extends and which encloses the space between the compressor andturbine rotor; and the centre bearing is mounted in a housing 9 carriedby a perforated partition it disposed towards the front end of theintermediate casing B. The partition as divides the casing into aforward portion H and a main rearward portion 12'.

The compressor which is generally indicated at is in the drawing,delivers compressed air to a number of combustion chambers one of whichis shown at it in the drawing and which are arranged in a circle roundthe casing 8;- and the products of the combustion flow from thecombustion chambers through a ring of fixed guide vanes 45 to the bladeslb of the rotor 6. The vanes 15 and blades l6 are enclosed by a fixedexternal shroud H while the guide vanes have a fixed internal shroud 58.The rotor has an internai shroud [9" for its blades and the two internalshrouds i8 and iii are arranged to minimise the escape of hot gasesthrough the clearance space between them.

The auxiliary compressor for cooling comprises a casing 21! mounted onthe front end of the intermediate casing 8 with its outlet 2| openinginto the front portion I I of the casing. The casing 20 contains acentrifugal impeller 22 secured on the driving shaft I. An air intake 23is provided through the intermediate casing between the fan casing 20and the casing of the compressor l3 and extends radially inwards to theeye of the impeller 22.

The centre bearing housing 3 and the rear bearing housing i are sodesigned that the cooling air can flow from the front portion II of theintermediate casing through the perforated partition 10 past the centrebearing housing to the main portion I2 of the casing and thence throughthe rear bearing housing I and then over the front face of the turbinerotor 6 to a space 24 within the fixed inner shroud It for the guidevanes. A cylindrical casing 25 extends from this shroud forwardly tomeet the frusto-conical wall of the intermediate casing 8 so as toenclose the space 24. A number of ducts, one of which is shown at 26 inthe drawing, are arranged to deliver cooling air from the space 24 tocool the outer fixed shroud [1.

It will be observed that the space 24 is enclosed 'partly by the turbinerotor 6 and partly by the inner fixed shroud N3 of the ring of fixedguide blades I5 through which the products of combustion flow to theblades of the turbine. The pressure of the cooling air delivered intothe space 24 by the action of the cooling fan therefore reduces thepressure drop through the clearance space between the shrouds l8 and 19so that the leakage of hot gases through this clearance space isreduced. Further any hot gas leaking through this clearance is carriedby the cooling air away from the rear main bearing 5.

It will be seen that the invention provides a simple arrangement forcirculating cooling air under pressure through the turbine structurewhich does not have the disadvantages of the known arrangement forpressure circulation referred to above and does not require acomplicated pipework installation which was found necessary with theknown arrangement.

I claim:

1. In combination in an internal combustion turbine engine a maincompressor rotor, a main compressor stator structure, a turbine rotor, aturbine stator structure, driving shaft connecting means between saidmain compressor rotor and said turbine rotor, combustion equipmentreceiving compressed air from said main compressor stator structure, anddelivering products of combustion to said turbine stator structure, anintermediate annular casing structure interconnecting said'maincompressor stator structure with said turbine stator structure andsurrounding said driving shaft connecting means, a turbine bearing forsaid turbine rotor supported within and by said intermediate casingstructure, an auxiliary compressor rotor carried on said driving shaftconnecting means, an auxiliary compressor stator structure within saidintermediate casing, an inlet duct to said auxiliary compressor statorstructure and discharge means therefrom, an exhaust outlet from saidintermediate casing on the side of said bearing remote from saidauxiliary compressor and communicating passages through the supportingstructure of said bearing between the discharge 4 means of saidauxiliary compressor and said exhaust outlet.

2. The combination of a gas-turbine, a main rotary compressor coaxialtherewith, a drivingshaft connecting said gas-turbine and saidcompressor, combustion equipment extending between said compressor andsaid turbine and arranged around said driving-shaft connection, anintermediate annular casing structure located axially between saidgas-turbine and said compressor, a turbine bearing for said gas-turbinesupported within and by said intermediate casing, an auxiliary rotarycompressor located within said intermediate casing and driven by saiddriving-shaft and arranged to discharge air under pressure into saidintermediate casing, an inlet duct for said auxiliary compressor, anexhaust outlet from said intermediate casing on the side of said bearingremote from said auxiliary compressor, and communicating passagesthrough the supporting structure of said bearing between the dischargeof said auxiliary compressor and said exhaust outlet.

3. A combination according to claim 2 further comprising a shaft-bearingfor said driving-shaft connection located within and supported by saidintermediate casing and located between said turbine-bearing and saidauxiliary compressor and having communicating passages through thesupporting structure of said shaft-bearing from the auxiliary compressorside thereof to the turbine-bearing side thereof.

ADRIAN ALBERT LOMIBARDl REFERENCES CITED The following references are ofrecord in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,595,278 Woerner Aug. 10, 19262,180,168 Puffer Nov. 14, 1939 2,243,467 Jendrassik May 27, 19412,401,826 Halford June 11, 1946 2,432,359 Streid Dec. 9, 1947 FOREIGNPATENTS Number Country Date 121,367 Great Britain Dec. 19, 1918 290,014Great Britain May 10, 1928 696,062 Germany Sept. 10, 1940

